A Study on Improving Waveform Fault Detection Coverage and a Multi-Layer Fault-Management System in a Guided-Weapon Radar

Purpose: This study analyzes a waveform fault that was not detected by existing inspection procedures and was identified following a mission failure during an actual guided-weapon firing. It also presents a mission- function-based, multi-layer fault management system.Methods: An empirical single-case study integrated FRACAS, functional FMEA, and RCM. Failure isolation proceeded by tracing the event time, mission phase, active function, signal path, and component. The improvements were evaluated through fault-injection tests, staged system verification, a fleet-wide inspection, and follow-up operational records.Results: The direct functional cause was the loss of Key code output from a direct digital synthesizer (DDS). Functional detection coverage increased from 0/6, based on a review of existing detection functions, to 6/6 in fault-injection tests. The detection–transmission–display path operated successfully in all 60 trials. Two additional defective units were identified and corrected among 47 inspected units. No mission failure attributable to the same RLRT waveform fault was observed during approximately three years of follow-up operation.Conclusion: This study provides a traceable framework linking failure evidence, maintenance-task selection, and testability improvement to address functional faults not detected by existing inspection procedures. The findings are limited to the defined complete waveform-loss conditions and do not establish a radar-wide statistical detection probability.